Cable tensostructure including stiffening latticed elements

ABSTRACT

A cable tensostructure including at least two pairs of cables, each pair being operative in a vertical plane, the planes being substantially parallel to each other, two pluralities of transverse members each comprising a latticed body of substantially prismatic configuration constituting a transverse connection between the pairs of cables while carrying the platform elements forming the runway plane along which the pedestrian and vehicular traffic move.

United States Patent 1 [111 3,758,905 Baratta 1 Sept. 18, 1973 [54] CABLE TENSOSTRUCTURE INCLUDING 2,622,546 12/1952 Kramrisch 14/19 X STIFFENING LAT-"CED ELEMENTS 2,642,598 6/1953 Beretta 14/18 Primary Examiner-Nile C. Byers, Jr. AttorneyEdward S. lrons et al.

[57] ABSTRACT A cable tensostructure including at least two pairs of cables, each pair being operative in a vertical plane, the planes being substantially parallel to each other, two pluralities of transverse members each comprising a latticed body of substantially prismatic configuration constituting a transverse connection between the pairs of cables while carrying the platform elements forming the runway plane along which the pedestrian and vehicular traffic move.

3 Claims, 11 Drawing Figures PATENTED SEN 3 I975 SHEET 5 OF 5 CABLE TENSOSTRUCTURE INCLUDING STIFFENING LATTICED ELEMENTS BACKGROUND AND SUMMARY OF THE INVENTION This invention relates to monoor multitensostructures arranged in multidirectional planes and including prismatic members of latticed or cage-like configuration designed for cooperating with said tensostructures to stiffen same.

The cage-like members are provided to support directly the elements of the platfonns or the stages of the roadways, footpaths or the like, which are subjected to incidental steady loads, live loads of various kinds, for instance, pedestrian and vehicular traffic, liquids moving in pipings or the like.

The invention comprises, in combination and cooperation, at least two pairs of cables, each pair being operative in a vertical plane, the planes of said pair being substantially parallel to each other, and two pluralities of transverse members, each consisting of a latticedor cage-like body of a substantially prismatic form which is designed to constitute a transverse connection between said pairs of cables, as well as to carry the platform elements forming the runway plane along which move the pedestrian and vehicular traffic as will be hereinafter indicated.

Each pair of cables, hereinafter referred to as elementary system," comprises a carrying cable and a stiffening carried cable. The cables are duly anchored to or simply supported by vertical elements, such as frameworks, piers, shoulders or the like. The ends of the carrying cables are always anchored or supported at heights higher than the ends of the carried cables are anchored. Each cable of an elementary system is longer than the length of the free span on which cable is stretched so that the cables of each pair can intersect at two points.

The cross points, except for particular purposes, are spaced apart the same distance from the respective less remote anchoring or supporting points.

The afore said latticed or cage-like members which are arranged between the pairs of cables of at least two cooperating and associated vertical elementary systems" force the cables to be spaced away from each other in a vertical plane, causing the carrying cables to take a concave form as viewed from the top, and the carried cables to take an opposite configuration, i.e. a convex form.

The two pluralities of cage-like members comprise a first plurality of cage-members designed to be inserted between the carrying and the carried cables in the intermediate portions of the structure between the two cross points, the members performing the following tasks:

a. Two tension the cables of each elementary system," also in the case of the action of reversible forces which can act upwardly or downwardly. The members are always subjected to substantially compression stresses.

b. To carry the elements of the platform or stages of the runways or the like which may be arranged in one or more levels.

c. To receive all the stresses from the stage or stages and to distribute uniformely the total load over the whole length of the carrying cables cooperating therewith; and, according to a reversability process, to receive the stresses acting from the bottom on the carrying cable and to uniformely distribute them on the carried cable, avoiding concentrated loads since the function of the cables is reversible.

d. To connect and link together in transverse direction two or more cooperating elementary systems." The second plurality of cage-like members are designed to be inserted between the portions of cables positioned between one cross point and the less remote anchoring or supporting point, i.e. at the outer sides with respect of the zone where are inserted the cage-like members of the aforesaid first plurality.

The cage'like members of this second plurality ac complish the same task as that described in the above paragraphs (b) and (d) but are also adapted to house tensioning means provided to directly connect the carrying and carried cables of each elementary system" in these zones.

Of course, during erection of the structure and tensioning of the cables, temporary or permanent means or devices are associated therewith in order to accomplish control and adjustment operations.

With reference to the tenso-structures designed for a pluridirectional embracing action, which are provided in cases of non-vertical stresses of considerable magnitude, as, for instance, in the case where very large spans are concerned, or when provision may be made for particularly high natural forces, the forces are counteracted by means of a transverse stiffening cable system which consists of one or more elementary systems" acting in one or more substantially horizontal planes, or along other differently inclined planes or surfaces which intersect each other with the most convenient angle according to the circumstances.

Prior art cable carrying systems provided to attain similar purposes are substantially as follows:

1. Suspended carrying systems which comprise one or more pairs of carrying cables arranged in vertical parallel planes and which are put in tension by the weight of a special latticed girder, from which are supported the stages and runways.

2. A tenso-structure system of the Jawert-type, wherein two substantially parallel pairs of cables are provided which are superposed and spaced away from one other in a vertical plane, and which are connected to each other by tie bars which are only subjected to traction stresses.

In the aforesaid solutions (1) and (2), the most difficult problem to be solved is that of obtaining a total stiffening of the structure in any direction. For lack of such a stiffening, repeated and rhytmical stresses due to live loads can cause an excessive dynamic strain which can produce dangerous fatigue phenomena in the materials used.

Difficults arise in the application in practice of the carrying system b); further it can be used only for limited and particular applications on account of its considerablc height and of the elasticity of this system which cannot be entirely controllable.

By connecting successively various elementary systems" of the present invention according to special configurations, a complex and organic structure can be obtained having nearly complete rigidity in all directions. The structure is also able to maintain considerable stability since the functionality of the carrying and stiffening elements is of a reversible character so that this structure can withstand any load or stress acting in whatever direction and sense.

This enables the tenso-structure of the invention to be suited to different conditions of load and span. The lightness of this structure further allows considerable increase in efficiency, i.e. the weight of the structure being the same, a higher live load can be supported by it, as compared with the live load which could be supported by known cable suspended structures.

As far as practice of the invention is concerned, it is point out that the tenso-structure of the invention is suitable to be produced by industrial processing in the broadest manner by prefabricating most parts of the various components and by their progressive and gradual setup, at first being installed the carrying cables by means of service cables and then successively being mounted the prefabricated cage-like or latticed members and at last the stiffening carried cables. Afterwards a gradual tensioning of the cables is performed in successive steps, in order to avoid that the carrying structure being overstressed in concentrated zones, but, on the contrary, in order to obtain that it is stressed evenly over its whole length.

The accompanying drawings show, merely by way of example, some embodiments of the invention applied to a bridge construction. In the drawings:

BRIEF DESCRIPTION OF THE DRAWINGS:

FIG. 1 is a diagrammatic side view of a first embodiment of the invention;

FIG. 2 is the top view thereof;

FIG. 3 is the top ,view of another embodiment wherein, instead of only two vertical elementary systems, there are three .elementary systems, the side view of this embodiment being the same as that shown in FIG. 1;

FIG. 4 is the cross sectional view taken along line X--X of FIG. 3;

FIG. 5 is a perspective view of a detail of the tensostructure at the central part of the bridge wherein the platform elements have been partly cut away and their superstructures omitted;

FIG. 6 is a perspective view similar to that of FIG. 5, illustrating an end portion of the bridge;

FIG. 7 is a side view of still another embodiment of a two stage bridge;

FIG. 8 is a diagrammatic horizontal longitudinal section taken along the plane wherein there is provided a horizontal elementary system provided to obtain more effective stiffening in the transverse direction of a bridge according to a further embodiment of the invention;

FIG. 9 shows another embodiment of the solution illustrated in FIG. 8;

FIGS. 10 and 11 show a side view and the top view, respectively, of a still further embodiment of the invention relating to a four-roadway bridge.

DETAILED DESCRIPTION OF THE PREFERRED I EMBODIMENT With reference to the drawings it is to be pointed out that like references designate corresponding parts throughout the several embodiments.

Each elementary system comprises a carrying cable 1 and a stiffening carried cable 2. In the simplest embodiment the carrying structure comprises at least two pairs of cables 1 and 2, each pair operating in a vertical plane, said vertical planes being substantially parallel to each other and to the vertical longitudinal centre plane YY of the bridge. More precisely there are two vertical elementary systems" in the embodiment of FIGS. 1 and 2 and 7 to 9 and three vertical elementary systems" in the embodiment of FIGS. 3 and 4. At 3 are generally indicated the cage-like or latticed members of the first plurality of cage-like members which are designed to withstand compression stresses and at 4 are generally marked the cage-like or latticed members which act in combination with tie means 5 (FIG. 6). The cables I and 2 are anchored to or are supported by stationary supporting elements 7 of known type, as piers, frameworks or the like; said cables may also extend beyond said support members 7 until anchored to the ground at points 6. The latticed members 3 act as spacing means as well as connecting means for transversely connecting the associated parallel vertical elementary systems of cables 1 and 2 forming the carrying structure. Each cage-like member 3 is constituted of vertical rods 3a (FIG. 5) acting as structs, of spacing transverse beams 3b set at a right angle to the said plane YY, and of longitudinal beams, the uppermost and the lowermost of which are duly shaped as will be hereinafter described and are marked 3c, while the intermediate longitudinal beams 3d are rectilinear. The cage-like members 3 are inserted in those portions of the cables 1 and 2/ between the two cross points 8 of said cables, said members 3 in the direction perpendicular to the plane Y- Y having a width not smaller than the distance between the or the outermost elementary systems, in the case where more than two vertical elementary systems are provided. The sides of the faces of the members 3 which are parallel to the plane Y-Y, as well as the upper and lower ones, can be braced together by bracing beams (not shown in the drawings), while the traverse faces must be at least partially open in order to enable the mounting of the platform or stage elements 9 of the bridge and to allow the free passage of the pedestrian and vehicular traffic. In FIG. 5 it can be seen that the elements 9 forming the platform or stage are supported by the beams 3d with the interposition of absorbers of any suitable type which are not shown in the drawings, said beams 3d being integral with the vertical rods 3a. Of course, in the case of a multi-stage bridge there are beams 3d at different heights. Further single members 3 could also be substituted by two or more members 3 superposed in column, the intermediate members 3 of said columns being constituted of cage-like or latticed parallelepiped elements rectangular in longitudinal vertical section. The platform elements 9 are preferably constructed of modular rectangular elements, the longer sides of which have a length equal to the width of the roadway increased with the width of the directional separators and of that of the side spaces to be used for the erection of parapets, or designed for the installation of pipings, for the construction of pedestrian side walks or for other similar purposes. The elements 9 are mounted with their longest sides positioned perpendicularly to the plane Y-Y, said elements 9 being connected to the beams 3d.

It is to be pointed out that the construction of the platform does not involve any peculiarly big problem, since said platform will have no carrying function in the tenso-structure and on account of the fact that it is not connected to any element in which may be induced considerable size changes due to the changes of temperature. Provision has been made that the modular elements 9 have a very limited width and that they are formed of materials having a small thermal expansion; further they will be connected to each other with the interposition of expansion joints according to a well known practice. As has hereinabove been stated they are supported by the beams 3d with the interposition of vibration dampers so that the vibrations transmitted to the platform elements 9 by the traffic are not transferred to the carrying structure and therefore this latter is not forced to oscillate at frequencies which, for resonance effect, could become dangerous for the stability and for the efficiency duration of said carrying structure.

As has hereinabove been stated, the members 3 besides acting as means for carrying steady and live loads which are transmitted to them through the platform elements 9 must also serve to connect to each other the cables of each elementary system operating in vertical planes which are parallel to the longitudinal centre plane Y-Y and also as means for tensioning the cables 1 and 2 and for evenly distributing the loads. For such last purpose the upper and lower elements 30 of each cage-like members 3 are longitudinally shaped to match the curving of the cables 1 and 2 in their tensioned operative state, in said elements 3c longitudinal grooves or the like being arranged suitably to hold and guide the cables 1 and 2 so that they always evenly contact said elements 3c.

Between the vertical rods 3a of two juxtaposed members 3 are further provided packing means 11 adapted to form a deformable joint device for the damping of the vibrations, said means being not described and illustrated in detail, since they are well known in the art.

The cage-like members 4 are substantially similar to the members 3 and the outline of their vertical section parallel to the plane Y-Y is yet such as to match the configuration taken by the cables 1 and 2 in their tensioned operative state. These members 4 are constructed as a cage and include parts which are designed according to the same principle as the corresponding ones which compose the cage-like members 3, except that the vertical posts 4a are at least partially hollow or suitably shaped as to be able to constitute housings where pass and are guided the tension or tie means 5.

During the construction steps at first the carrying cables l are stretched; to these latter are then overhung temporarily the cage-like members 4 and on them are mounted the central cage-like members 3. The stiffening cables 2 which pass under the members 4 are then stretched and upon the members 3, afterwards a first tensioning step is carried out. After having correctly positioned each of the members 3 and 4, the tie means 5 are duly put in tension with the use of known means and devices. Thence will be completed the tensioning and the anchoring of the cables 1 and 2 so that the tenso-structure attains its operative arrangement with the desired transverse stiffening. Subsequently the plat form elements 9 are mounted which are connected to the beams 3d and 4d respectiveky with the interposition of vibration dampers.

Of course, after having completed the entire superstructure of the bridge further final adjustment of the tension of the cables can be performed.

It will be apparent that the tensioning cage-like members 3 and 4 can be also mounted in the zones between the piers 7 and the anchoring points 6 at the sides ofthc river, lake, sea, or valley.

In the embodiment of FIGS. 3 and 4 two roadways 9 are provided, placed side by side, and supported by three vertical elementary systems" parallel to each other. In the embodiment of- FIG. 7 two parallelely superposed platforms 9a and 9b are provided which are supported by two vertical "elementary systems. Of course, in this case the vertical rods 30 and 4a of the members 3 and 4 must have such a height as to be able to carry the beams 3d and 4d for the anchoring of the elements 9a and 9b of the two platforms or stages.

Now referring to the horizontal sectional views shown in FIGS. 8 and 9, in these views these may be seen the use of a substantially horizontal elementary system which is preferably arranged near the plane of the central platform, said horizontal elementary system comprising a pair of cables 1 and 2 which act in the same manner as the cables 1 and 2 of the aforesaid vertical elementary systems." In this case, however, as spacing means in the areas intermediate the cross points 8 can be used portions of the same members 3 and optionally 4 which are mounted in the same zones for spacing away from each other the cables 1 and 2 of the vertical elementary systems; and for this purpose in the beams 30 and/or 3b means are provided in suitable positions, adapted to serve for the connection and the tensioning of the cables 1 and 2 of this substantially horizontal elementary system," while in the outer zones, i.e. where the areas defined between the cables 1 and 2 of this system has a convex outline form, tie rods 5 are provided which may be independent from each other. In the variant of FIG. 9 the simple horizontal elementary system" is substituted by two horizontal elementary systems" arranged in series; in this case in the section where the two horizontal elementary systems" are jointed to one other a strong traverse beam 10 is arranged to which said two elementary systems" are both anchored which are constructed as has been described with reference to FIG. 8.

Said transverse elementary systems" could also extend not only in a plane, but also along a cylindrical surface: for such a purpose anchoring means are arranged in the lattice members 3 and 4 so positioned as to force the cables 1 and 2 of each transversely operating elementary system into a curved configuration, wherein the heights of the cable portions decrease from the centre of the span moving towards the piers 7. Further, the cables 1 and 2 of the transverse elementary systems" could move away from each other outwardly beyond the vertical elementary systems as they get near the piers 7 so as to increase the bridge cross-section near the piers 7 in particular in the case of large or very large spans.

It will be apparent that the carrying tenso-structure as hereinbefore described and illustrated can be repeated between each pair of a plurality of piers arranged in series in order to construct a bridge of two or more successive spans.

In the variant of FIGS. 10 and 11 the bridge is supported by frame-works 7a and the prismatic latticed members 4 are substituted by latticed members 4' of a modified form.

I claim:

1. A cable tensostructure, comprising a pair of elementary systems, each of said systems comprising a carrying cable and a carried cable, said cables being positioned in a vertical plane and intersecting each other at two distinct points, means anchoring the ends of said carrying cables, means anchoring the ends of said carried cables at points lower in elevation than the points where the ends of said carrying cables are anchored, a plurality of cage-like members positioned between said carried and carrying cables connecting and stiffening same, said cage-like members being prismatic in configuration and generally complementary in configuration with respect to said carrying and carried cables, certain of said cage-like members being located between said distinct points of said cables so as to function as struts while others of said cage-like members being positioned between said distinct points of intersection and said means anchoring the ends of said cables, said others of said cage-like members including means for adjusting the tension of said cables, the width of said cage-like members being greater than the distance between said pairs of cables, platform elements and means supporting said platform elements within said cage-like members.

2. A cable tensostructure as in claim 1, including thermal joint means positioned between said platform elements and said cage-like members.

3. A cable tensostructure as in claim 7, including additional cables disposed in a substantially horizontal plane and intersecting each other at two distinct points, the ends of said two additional cables being anchored by supporting means, certain of said cage-like members being located so as to space said additional cables apart from one another except at said points of intersection and means tensioning said additional cables also forming a part of certain of said cagelike members. 

1. A cable tensostructure, comprising a pair of elementary systems, each of said systems comprising a carrying cable and a carried cable, said cables being positioned in a vertical plane and intersecting each other at two distinct points, means anchoring the ends of said carrying cables, means anchoring the ends of said carried cables at points lower in elevation than the points where the ends of said carrying cables are anchored, a plurality of cage-like members positioned between said carried and carrying cables connecting and stiffening same, said cagelike members being prismatic in configuration and generally complementary in configuration with respect to said carrying and carried cables, certain of said cage-like members being located between said distinct points of said cables so as to function as struts while others of said cage-like members being positioned between said distinct points of intersection and said means anchoring the ends of said cables, said others of said cage-like members including means for adjusting the tension of said cables, the width of said cage-like members being greater than the distance between said pairs of cables, platform elements and means supporting said platform elements within said cage-like members.
 2. A cable tensostructure as in claim 1, including thermal joint means positioned between said platform elements and said cage-like members.
 3. A cable tensostructure as in claim 7, including additional cables disposed in a substantially horizontal plane and intersecting each other at two distinct points, the ends of said two additional cables being anchored by supporting means, certain of said cage-like members being located so as to space said additional cables apart from one another except at said points of intersection and means tensioning said additional cables also forming a part of certain of said cage-like members. 